This application claims the priority of German Application No. 103 04 299.7 filed on Feb. 4, 2003, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an internally ventilated brake disk comprising two friction rings which are mutually connected by way of webs ducts for conducting cooling air being formed between the webs and the two friction rings with the webs extending in a curved manner between their end regions.
Internally ventilated brake disks with curved cooling air ducts are known. Thus, French Patent Document FR-PS 11 80 373 shows an internally ventilated brake disk for a retarder brake with cooling air ducts which are curved in a blade-type manner. From German Patent Document DE 22 57 176 C3, a brake disk is known for a friction brake which also has curved cooling air ducts. In addition, perforations for improving the braking effect in wetness and an improved cooling effect are provided here in the friction disks.
Based on this state of the art, it is an object of the invention to create an internally ventilated brake disk which is improved with respect to the rate of air flow for the brake disk cooling and with respect to the strength of the brake disk.
This object is achieved according to certain preferred embodiments of the invention by providing an internally ventilated brake disk comprising two friction rings which are mutually connected by way of webs ducts for conducting cooling air formed between the webs and the two friction rings extending in a curved manner between their end regions, wherein end regions of the webs pointing to an outer circumference area of the brake disk are aligned essentially radially to the brake disk, wherein end regions of the webs pointing to an inner circumference side of the brake disk are set at an angle of from 20° to 70°, with respect to a tangent ray which is applied to this point on the brake disk and points against a rotating direction of the brake disk. In the case of a brake disk, which comprises two friction rings mutually connected by way of webs, it is suggested according to the invention to construct the curved webs such that they are essentially radially aligned at the outer circumference of the brake disk, while, at the inner circumference of the brake disk, that is, in the region of the cooling air entry, they are sloped by an angle of from 20° to 70° with respect to a tangent placed at this point of the inner circumference against the rotating direction of the brake disk. According to certain preferred embodiments this angle at the entry side amounts to 30° to 60° with respect to the tangent.
The invention is based on the recognition that a radially aligned web in comparison to differently aligned webs has the highest strength. Since this measure is applied in the region of the outer circumference of the brake disk, which is particularly stressed by the rotation of the brake disk, the effect of this strength-increasing measure is particularly great.
Furthermore, advantageously, the highest static pressure increase can be achieved according to preferred embodiments of the invention by means of a radially ending web by way of a cooling duct formed between the webs. A high static pressure increase is a prerequisite for creating a rate of air flow which is as high as possible for cooling the brake disk.
The entry angle, that is, the angle of the end region of the webs pointing to the inner circumference of the brake disk, is selected such that the initial direction of the web coincides as well as possible with the direction of the approaching cooling air in order to achieve a rate of air flow in this manner which is as high as possible.
Advantageous further developments of the invention are described below and in the claims.
It is suggested according to certain preferred embodiments of the invention that some of the webs be constructed as so-called primary webs, these primary webs forming fastening eyes on their end region facing the inner circumference of the brake disk. These fastening eyes are used for receiving fastening devices, for example, screwed connections for connecting the brake disk with a brake chamber, a wheel bearing or the like. Secondary webs are arranged between the primary webs and are used mainly for the air conduction and the mutually supporting of the two friction rings. Their end region facing the inner circumference of the brake disk is set back with respect to the end region of the primary webs in order to keep the cross-sectional surface for the entry of the cooling air available at the inner circumference of the brake disk as large as possible.
Furthermore, it is suggested according to certain preferred embodiments of the invention to ensure the overlapping of the webs in the radial direction of the brake disk by the selection of the parameters
number of webs (mainly primary and secondary webs)
selection of the entry angle of the webs and
selection of the width of the webs.
In addition, tertiary webs may be provided according to certain preferred embodiments of the invention which, in particular, are arranged in the region of the brake disk pointing to the outer circumference. Their end region facing the inner circumference of the brake disk is set back with respect to the end region of the secondary webs in order not to impair the cross-sectional surface available in the air ducts. The tertiary webs further improve the axial supporting of the friction rings, and, in this manner, the bending of the friction rings is reduced under the forces which are axially applied to the brake disk by means of the brake pads during the braking operation.
Furthermore, additional webs can be provided according to certain preferred embodiments of the invention. Such a requirement exists particularly if the axial support of the friction rings is to be further improved. Also, by means of additional webs, the surface in the air ducts can be increased which is effective for the cooling. Instead of additional webs, ribs may also be provided which extend from the interior sides of the friction rings into the air ducts.
To the extent that perforation bores are provided in the friction rings, these are arranged in one or two rows approximately parallel to the webs inside the air ducts according to certain preferred embodiments of the invention. In this case, the perforation bores are preferably arranged away from the flank of the webs pointing in the rotating direction of the brake disk, since on this flank, viewed in the circumferential direction, in each case, the highest pressure increase takes place in the air duct, which pressure increase is not to be impaired by perforation bores. In addition, preferably in the area of the highest static loads in the friction rings, that is, in the proximity of the inner circumference of the brake disk, no more perforation bores are arranged in the air duct. As a result of this measure, the risk of cracks can be reduced in this particularly stressed area.
According to certain preferred embodiments of the invention, especially for brake disks made of a fiber-reinforced composite material, for example, made of a silicon-infiltrated carbon-fiber-reinforced carbon C/CSiC (compare German Patent Document DE 44 38 455 (corresponding U.S. Pat. No. 6,086,814)), it is suggested, for reasons of strength, to select the wall thickness of the webs to be at least 10 mm and to design the fastening eyes of the webs such that the outside diameter of the fastening eyes is at least twice as large as its inside diameter. This contributes to the improved stability of the brake disk and to the improved strength of the linking of the brake disk.
The above-described construction principles can be used for internally ventilated brake disks, generally irrespective of their construction type. They can therefore be applied particularly to brake disks constructed in one or two parts and to a variety of materials, particularly for gray cast iron and composite ceramics, such as C/CSiC, and carbon fiber reinforced carbon.
In the following, the invention will be explained in detail by means of an embodiment illustrated in the figures.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.